In recent years, developed have been liquid crystal display devices that perform three-dimensional (3D) display by letting the right and left eyes of an observer visually recognize images viewed from different points of view thereby giving parallax, and some of such devices have been commercialized.
Among such liquid crystal display devices, there is one where a parallax barrier having light-transmitting regions and light-shielding regions formed alternately in a striped shape is combined with a liquid crystal display panel. With this parallax barrier, specific viewing angles are respectively given to a right-eye image and a left-eye image displayed by the liquid crystal display panel, whereby images corresponding to the right eye and the left eye are made visually recognizable if only viewed in a specific observation range in the space. Thus, an observer can recognize 3D display without the necessity of using a visual aid such as a filter system.
Moreover, there is known a 2D/3D switchable liquid crystal display device where a means for enabling or disabling the parallax barrier function is realized by a switching liquid crystal panel to permit switching between 3D display and two-dimensional (2D) display (see Patent Document 1, for example).
The switching liquid crystal panel is constituted by a pair of substrates bonded together with a frame-shaped sealing material and a liquid crystal layer sealed inside the frame of the sealing material. On the inner surfaces of the substrates constituting the switching liquid crystal panel facing each other, switch electrodes for switching of the parallax barrier function are provided in a parallax barrier region corresponding to a display region. A lead interconnect is connected to each switch electrode with one end thereof lying on the switch electrode. The lead interconnect extends through a frame region outside the parallax barrier region to be led up to a substrate edge. The lead tip end constitutes an external connection terminal, via which the lead interconnect is connected to an external circuit.
Recently, also, for display devices such as liquid crystal display devices, a touch panel has been widely used, which is placed on a display panel to serve as an input device for inputting information into the display device by performing various types of operations on the display screen using a finger, a pen, etc.
Such touch panels are classified, according to the operating principle, into ones of a resistive film method, a capacitive method, an infrared method, an ultrasonic method, an electromagnetic induction method, etc. Among others, a capacitive touch panel is known suitable for display devices because it comparatively less impairs the optical characteristics of display devices.
A capacitive touch panel has touch detection electrodes for touch position detection in a touch region corresponding to the display region. A lead interconnect is connected to each touch detection electrode with one end thereof lying on the touch detection electrode. The lead interconnect extends through a frame region outside the touch region to be led up to a substrate edge. The lead tip end constitutes an external connection terminal, via which the lead interconnect is connected to an external circuit.
In the switching liquid crystal panel and touch panel described above, the regions (parallax bather region and touch region) corresponding to the display region must be transparent to make the display image visually recognizable. Therefore, the switch electrodes and touch detection electrodes located in such regions are formed of a transparent conductive oxide such as indium tin oxide (ITO). On the other hand, the lead interconnects located in the region corresponding to the non-display region do not have to be transparent because they do not block the display image. As the material thereof, therefore, a high-melting metal such as titanium (Ti) and molybdenum (Mo) is suitably used for prevention of electrolytic corrosion reaction at the connection with the switch electrodes and touch detection electrodes made of a transparent conductive oxide (see Patent Documents 2 and 3, for example).